<template>
  <div class="spec-preview">
    <img :src="skuImageList[defaultIndex]?.imgUrl" />
    <div class="event" @mousemove="moveMask"></div>
    <div class="big" >
      <img :src="skuImageList[defaultIndex]?.imgUrl" ref="big"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  data() {
    return {
      defaultIndex: 0,
    };
  },
  props: ["skuImageList"],
  mounted() {
    this.$bus.$on("getZoomIndex", (index) => {
      this.defaultIndex = index;
    });
  },
  methods: {
    moveMask(e) {
      //鼠标位置-蒙版的一半
      //获取鼠标位置
      const mouseOffset = {
        left: e.offsetX,
        top: e.offsetY,
      };
      //蒙版大小的一半
      const mask = {
        width: this.$refs.mask.offsetWidth / 2,
        height: this.$refs.mask.offsetHeight / 2,
      };

      //获取蒙版位置
      const maskOffset = {
        x: mouseOffset.left - mask.width,
        y: mouseOffset.top - mask.height,
      };
      //边界值
      if (maskOffset.x < 0) {
        maskOffset.x = 0;
      }
      if (maskOffset.x >= e.target.clientWidth - this.$refs.mask.offsetWidth) {
        maskOffset.x = e.target.clientWidth - this.$refs.mask.offsetWidth;
      }
      if (maskOffset.y < 0) {
        maskOffset.y = 0;
      }
      if (
        maskOffset.y >=
        e.target.clientHeight - this.$refs.mask.offsetHeight
      ) {
        maskOffset.y = e.target.clientHeight - this.$refs.mask.offsetHeight;
      }

      //蒙版的移动距离
      this.$refs.mask.style.left = maskOffset.x + "px";
      this.$refs.mask.style.top = maskOffset.y + "px";

      //移动的比例
      const scale = {
        x: e.target.offsetWidth / this.$refs.big.offsetWidth,
        y: e.target.offsetHeight / this.$refs.big.offsetHeight,
      };
      //大图的移动距离
      this.$refs.big.style.left = -maskOffset.x / scale.x + "px";
      this.$refs.big.style.top = -maskOffset.y / scale.y + "px";
    },
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>